The present invention generally relates to inkjet and other types of printers and more particularly, to a novel printing system for improving the lightfastness of printed documents produced by a color printer. The present invention includes a preprogrammed lightfastness scheme that can be incorporated in an inkjet printhead for improving lightfastness of printed documents produced by a color printer, such as an inkjet printer.
Inkjet printers are commonplace in the computer field. These printers are described by W. J. Lloyd and H. T. Taub in xe2x80x9cInk Jet Devices,xe2x80x9d Chapter 13 of Output Hardcopy Devices (Ed. R. C. Durbeck and S. Sherr, San Diego: Academic Press, 1988) and U.S. Pat. Nos. 4,490,728 and 4,313,684. Inkjet printers produce high quality print, are compact and portable, and print quickly and quietly because only ink strikes a printing medium, such as paper.
An inkjet printer produces a printed image by printing a pattern of individual dots at particular locations of an array defined for the printing medium. The locations are conveniently visualized as being small dots in a rectilinear array. The locations are sometimes xe2x80x9cdot locationsxe2x80x9d, xe2x80x9cdot positionsxe2x80x9d, or pixelsxe2x80x9d. Thus, the printing operation can be viewed as the filling of a pattern of dot locations with dots of ink.
Inkjet printers print dots by ejecting very small drops of ink onto the print medium and typically include a movable carriage that supports one or more print cartridges each having a printhead with ink ejecting nozzles. The carriage traverses over the surface of the print medium. An ink supply, such as an ink reservoir, supplies ink to the nozzles. The nozzles are controlled to eject drops of ink at appropriate times pursuant to command of a microcomputer or other controller. The timing of the application of the ink drops typically corresponds to the pattern of pixels of the image being printed.
In general, the small drops of ink are ejected from the nozzles through orifices or nozzles by rapidly heating a small volume of ink located in vaporization chambers with small electric heaters, such as small thin film resistors. The small thin film resistors are usually located adjacent the vaporization chambers. Heating the ink causes the ink to vaporize and be ejected from the orifices.
Specifically, for one dot of ink, a remote printhead controller, which is usually located as part of the processing electronics of the printer, activates an electrical current from an external power supply. The electrical current is passed through a selected thin film resistor of a selected vaporization chamber. The resistor is then heated for superheating a thin layer of ink located within the selected vaporization chamber, causing explosive vaporization, and, consequently, a droplet of ink is ejected through an associated orifice of the printhead.
However, in many inkjet printers, lightfastness is a problem where the document that is printed is exposed to high or prolonged fluxes of lights. As a result, color documents usually fade over time and become unpleasant. Also, since each ink color can have a different lightfastness, documents that contain different colors often fade unevenly. This causes an unattractive document because certain portions of the color document are faded more than other portions. One way that this problem has been addressed was with the development of inks with improved lightfastness. However, these inks can be expensive, are prone to failure and require larges amounts of development time.
Therefore, what is needed is an inexpensive and effective printing system for improving the lightfastness produced by a color printer without altering ink formulas or adding additional materials to stabilize a printed document. What is additionally needed is a preprogrammed lightfastness scheme that can be incorporated in a printer driver for a color printer for improving the lightfastness of the color printout. What is further needed is an inexpensive and effective printing system with balanced fading of color printouts.
To overcome the limitations in the prior art described above, and to overcome other limitations that will become apparent upon reading and understanding the present specification, the present invention is embodied in a printing system for improving the lightfastness of printed documents produced by a color printer. The present invention includes a preprogrammed lightfastness scheme that can be incorporated in any suitable color printer, such as an inkjet printer, for improving lightfastness of printed documents.
In general, the present invention can include an inkjet printhead assembly that incorporates a preprogrammed lightfastness scheme directly into the printer driver for selectively improving color documents produced by an inkjet printer. A general lightfastness scheme can be developed for each class of inkjet printhead assemblies before, during or after manufacturing of the class of inkjet printhead assemblies.
The lightfastness scheme could include a printing pattern for each color of the inkjet printhead. The printing pattern would be based on the general lightfastness that exists for each color. The printing pattern could be any suitable method for improving lightfastness of the color. For example, a predefined number of extra layers of a certain color ant could be printed during printing of that color ant based on empirical data collected regarding the colorant""s optical density.
The lightfastness scheme can be controlled by a printer driver as software operating on a computer system that is connected to the inkjet printer or as firmware incorporated into the printer in a controller device. Also, the lightfastness scheme can be encoded on a memory device incorporated into inkjet printhead assembly itself. In this case, the memory device could also store other various printhead specific data. The data can include identification, warranty, characterization usage, empirical data regarding each colorant""s optical density, etc. Information and can be written and stored at the time the printhead assembly is manufactured. The lightfastness scheme can be accessed and applied by the printer driver.
In another embodiment, the inkjet printhead assembly includes a distributive processor that has the ability to apply the lightfastness scheme during printing operations. The distributive processor can receive the lightfastness scheme from the memory device or from the printer driver. The distributive processor can make other decisions, such as making its own firing decisions for providing lightfastness control and for producing documents that will have colors that fade evenly. For example, the distributive processor can be preprogrammed to regulate the number of extra layers that are to be printed for certain colorants, depending on the quality of print and lightfastness desired by a user. In addition, the distributive processor can aid in calibrating the printhead assembly in real time.
The printing system can also include an ink supply device having its own memory and can be fluidically coupled to the printhead assembly for selectively providing ink to the printhead assembly when necessary.